1. Field of the Invention
The present invention relates to the field of liquid crystal display, and in particular to a structure of backlight module.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and the liquid crystal molecules are controlled to change direction by application of electricity to the glass substrates in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module comprises a backlighting source of an LED light bar arranged at an edge of a backplane that is located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face of the light guide plate and, after being reflected and diffused, is projected out through a light emergence face of the light guide plate to form a planar light source for the liquid crystal panel.
Referring to FIG. 1, a conventional LED based side-edge backlight module comprises a backplane 100, a backlight source 300 arranged inside the backplane 100, a light guide plate 500 arranged inside the backplane 100 to correspond to the backlight source 300, a reflector plate 700 arranged on a bottom surface of the light guide plate 500, and optic films 900 arranged on a top surface of the light guide plate 500. The light guide plate 500 is made of a material of polymethylmethacrylate (PMMA) or methacrylate-butadiene-styrene copolymer (MBS), which has a light weight and better mechanical strength. In the conventional structure, the upper side of the backplane 100 is positioned against the reflector plate 700 and the upper side of the reflector plate 700 is tightly positioned against the light guide plate 500. This arrangement causes the backplane 100, the reflector 700, and the light guide plate 500 to physically engage and rub each other in mechanical vibration and impacts. Further, due to influence caused by the assembling environment, foreign objects may be trapped between the reflector plate 700 and the light guide plate 500 during the process of assembling. The foreign objects may rub the light guide plate 500 and the reflector plate 700 in mechanical vibration and impacts. This may easily result in scratching of the light guide plate thereby showing white spots or white staining on the screen. Problems of optic quality may thus result, deteriorating the displaying quality of the liquid crystal display device using such a backlight module.